Seed-eaters with toothless beaks (illustrated) outlived the dinosaurs because of their diet

Pecking at seeds may have helped ancestors of modern birds survive the cataclysm that wiped out the dinosaurs, scientists believe.

Small bird-like dinosaurs vanished along with giants such as Tyrannosaurus and Triceratops after a huge meteor smashed into the Earth 66 million years ago.

But some of them survived until the end of the Cretaceous period and instead evolved into the birds that populate the world today.

They were the seed-eaters with toothless beaks, new evidence suggests.

The theory could explain why no bird alive today has a beak lined with teeth.

Lead researcher Derek Larson, from the University of Toronto in Canada, said: ‘The small bird-like dinosaurs in the Cretaceous, the maniraptoran dinosaurs, are not a well-understood group.

‘They're some of the closest relatives to modern birds, and at the end of the Cretaceous, many went extinct, including the toothed birds - but modern crown-group birds managed to survive the extinction.

‘The question is, why did that difference occur when these groups were so similar?’

The scientists began their investigation by analysing collected data on more than 3,000 fossilised teeth from four different maniraptoran families - a clade of dinosaurs that includes birds.

They found maniraptoran diversity continued right up to the end of the Cretaceous, suggesting a sudden extinction due to a catastrophic event.

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The team suspected that diet might have played a part in the survival of lineages that produced today's birds.

Using published research about modern birds, including dietary information and inter-species relationships, the scientists inferred what their Cretaceous cousins might have eaten.

Pecking at seeds may have helped ancestors of modern birds survive the cataclysm that wiped out the dinosaurs (illustrated), scientists believe

They hypothesised in the study published in the journal Current Biology that the last common ancestor of today's birds was a toothless seed-eater with a beak.

‘Some groups of beaked birds may have been able to survive the extinction event because they were able to eat seeds,’ Mr Larson said.

The massive asteroid or comet strike would have temporarily altered the Earth's climate and blotted out the sun with dust.

Widespread vegetation loss would have robbed many plant-eating animals of their food source, and in turn large predators would have gone hungry.

But hardy seeds may have sustained the small toothless birds until the world began to recover.

WERE DINOSAURS ALREADY ON THEIR WAY OUT BEFORE THE ASTEROID?

They ruled the Earth for more than 180 million years before apparently disappearing in a catastrophic asteroid impact.

But the dinosaurs may have been teetering on the edge long before the impact from space that has been credited with wiping them out 66 million years ago, according to a new study.

Researchers suggest the kings of the prehistoric world had in fact been been in a state of decline for millions of years, and that a lack of diversity may have ultimately led to their extinction.

New statistical analysis suggest that dinosaurs may have been in a state of decline for millions of years before the asteroid strike 66 million years ago, and that a lack of diversity may have ultimately led to their extinction

While many believe the dinosaurs were going strong right up to the asteroid impact, the new analysis suggests that they may have already been dwindling for up to 50 million years earlier.

Indeed, the researchers say their slow demise may have enabled the earliest mammals to diversify just enough to be primed and ready to step into the gap left by the reptiles when the asteroid hit.

Using statistical analysis of the dinosaur family tree, researchers from the universities of Reading and Bristol carried out a study to compare the evolutionary dead ends against the fossil record.

Rather than going strong right up to the world-changing asteroid impact, their analysis showed that the number of new species of dinosaur emerging couldn't keep up with those dying out, so dinosaurs were becoming less diverse overall.

The analysis revealed that there were a few dinosaurs which bucked the declining trend. Hadrosaurs, the 'sheep or rats' of the dinosaur world, became more specialised and were branching off into new species at a higher rate than going extinct. Pictured are Parasaurolophus, which emerged more than 76 million years ago

This reached a critical point almost 24 million years before the asteroid hit, when species were becoming extinct at a faster rate than new ones were coming into existence.

Dr Chris Venditti, an evolutionary biologist at the University of Reading and senior author of the study, told MailOnline: 'What that means is that up to 50 million years before the dinosaurs went extinct because of the asteroid impact, the rate of speciation had fallen behind the rate of extinction.

'They were starting to dwindle, dinosaurs couldn't replace themselves with new species at the rate at which they were dying out.'

'That goes in the face of… all the other evidence which has been proposed for the scenario in which they were reigning strong right up until the time of the impact.'